Accurate measurement of serum gentamicin levels is critical for optimal patient care because of the low toxic-therapeutic ratio of gentamicin. Sera of some patients receiving gentamicin are icteric, and occasionally a critical sample from a patient receiving gentamicin is somewhat hemolyzed. It is sometimes necessary, therefore, to measure gentamicin levels on hemolyzed or icteric sera. This study will assess the capacity of our enzyme immunoassay procedure to measure gentamicin levels accurately on icteric and hemolyzed sera.